To be frank, contextual ads would be your best option and adsense would lead the way. However, you may want to feature affiliate programs, amazon or others that carry stocks of not only the smartwatch that you may have featured, but also other related brands.

Get their email. Build that up.
Let them know when the product is released and monetize them in the future as well.
Until product release maybe you can try to promote some related products with amazon.

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